Effects of Reusing Ti-6Al-4V Powder in a Selective Laser Melting Additive System Operated in an Industrial Setting

Abstract

Cost control and quality of additive manufactured (AM) components are critical characteristics for the success of this technology for industrial applications. Understanding how the virgin powder changes in terms of chemistry and physical properties with reuse cycles provides important information that can be translated into cost-effective practices for managing recycled powder. In this study, we focused on an industrial AM setting, where different numbers of components were printed on each build. A single lot of powder was reused for manufacturing a total of 31 builds using a selective laser melting additive system. The effects of reuse cycles on the characteristics of Ti-6Al-4V extra low interstitial powder were evaluated, during and prior to the printing process, by means of particle size distribution, tap density, flowability, powder morphology, and chemical composition. Additionally, chemical analysis and tensile testing of solid bars in the hot isostatically pressed (HIP) condition were evaluated in relation to powder reuse times. After reusing the powder for 31 times, it was found that the oxygen content increased to a maximum of 0.13 wt.%, whereas nitrogen, aluminum, and vanadium remained stable. The powder exhibited surface coarsening, and although some elongated/irregular particles were observed, mostly spherical powder particles with fewer satellites were present. Flowability improved, and tap density showed a slight decline with reuse times. No detrimental effect was found on the tensile properties of solid material postprocessed using HIP.